Asked to debate whether Edward Snowden is "a patriot or a traitor" during an event at the UCLA School of Law, Bruce Fein, the attorney representing all of us in a class-action suit against the NSA, remarked on the spirit of the Fourth Amendment.

"Patriotism was defined by Thomas Paine at the founding as a citizen who protects his country from his government," he began, "and I think that if we look at the Fourth Amendment as part of what this country is about, we see that he certainly seems to fit on that side more than treason."

Then he delved much deeper:

If we go back to the understanding of why we declared independence from Great Britain, it stemmed from worries about excessive surveillance. James Otis in 1761 was denouncing general writs of assistance, general search warrants, as being totally inimical to freedom and independence .... It empowered every petty official to go examine people's homes and businesses, to determine whether they had any smuggled goods. There was no probable cause.

... This opposition triggered, in John Adams's words, the spark that led to the American revolution .... The spirit of the Fourth Amendment, the spirit of the country, was captured in William Pitt the Elder's address to the British parliament in 1763, when he was opposing excise taxes, which also would be enforced by these general writs of assistance. And what he said rang throughout the colonies: The poorest man in his cottage may bid defiance to all the forces of the crown. He may be frail. The roof may shake. The winds may blow through it. Storms may enter. Rain may enter. But the King of England cannot enter. All his forces dare not cross the threshold of the ruined tenement."

That, ladies and gentlemen, was the spirit of the Fourth Amendment. It was later described by Justice Louis Brandeis in Olmstead v. the United States as the right to be let alone—the most cherished right among civilized people. And he understood that our right to that liberty, it applies because we're human beings and individuals. We don't have to justify the right to be let alone.

It's there because we live and we breathe.

The government has an obligation to explain why it can disturb that right. That's what America is about. And in my judgment, the NSA's program that Mr. Snowden disclosed has it inverted. The NSA's attitude, even with the concession that it has foiled no terrorism plots, despite gathering this telephony metadata for eight years, is, "Aha! True enough. But we need to continue. Because now we have a comfort level that there's nothing to discover. So we keep spying on innocent people in order to receive that assurance."

Well, that's an odd argument. Maybe we should have the NSA or FBI go search the closets of every home in the United States, hoping that maybe Osama bin Laden's cousin will be there. And if they discover nothing, it will be fully justified .... Now that certainly is not the Fourth Amendment that the United States adheres to, not the Fourth Amendment that the Senate intelligence committee and the House intelligence committee should be upholding.

The Fourth Amendment was being eroded long before the NSA began its current program of spying on millions of innocent Americans. The War on Drugs alone has done tremendous violence to it. But even when paramilitary SWAT units are kicking down doors in the dead of night because a homeowner is suspected of possessing marijuana—an atrocious practice that I've condemned on many occasions—they can at least say that they suspect the individualized target of an actual crime.

With its telephony-metadata program, the NSA sets the precedent that the state may force its way into the private affairs of citizens even when authorities themselves acknowledge that they are suspected of no crime. It's a dangerous, radical notion that national security statists have managed to pass off as centrism. Clear-eyed critics like Fein are vital if this trend is to be reversed before grave damage is done.

Conor Friedersdorf is a staff writer at The Atlantic, where he focuses on politics and national affairs. He lives in Venice, California, and is the founding editor of The Best of Journalism, a newsletter devoted to exceptional nonfiction.